1. Field of the Invention
This invention relates to a legged mobile robot control system, particularly to a legged mobile robot control system that controls the robot to walk with a human being with hand in hand.
2. Description of the Related Art
There has hitherto been proposed a robot which is configured to be capable of shaking hands with a human being, as taught by Japanese Laid-Open Patent Application No. 2004-283975, for example. This prior art robot mentioned in this reference has hands embedded with pressure-sensitive sheets for detecting the grasping force of the human being at handshaking and is controlled to change the contents of utterance and motion of arms in response to the detected grasping force. For example, this robot is controlled to utter as “Nice to meet you”, when the grasping force is moderate, but is controlled to utter as “Ouch” and to draw in the arm when the grasping force is excessive, thereby enabling to establish communication with human beings. This robot mentioned in the reference comprises a body like a human's upper body mounted on wheels.
Examples to establish communication with human beings will involve not only shaking hands with a human being, but also walking with hand in hand, i.e., walking while taking a human being's hands or walking while its hand being taken by a human being. When the robot comes into contact with a human being in this manner, like handshaking, the robot receives an external force of a considerable amount from him/her.
Since the robot mentioned in the reference is a wheeled robot, the external force acting through its arm will not cause the robot to lose stability unless the external force is quite large. However, in the case of a legged mobile robot such as a biped robot, the external force may sometimes be a disturbance enough to cause the legged mobile robot to lose stability. Thus the legged mobile robot is likely to lose stability when coming into contact with a human being.